Solar cell and solar cell module

ABSTRACT

A solar cell and a solar cell module are disclosed. The solar cell includes a substrate of a first conductive type, a plurality of emitter layers of a second conductive type opposite the first conductive type, a plurality of first conductive members partially connected to the substrate, and a plurality of second conductive members partially connected to each of the plurality of emitter layers.

This application claims priority to and the benefit of Korean PatentApplication No. 10-2009-0020532 filed in the Korean IntellectualProperty Office on Mar. 11, 2009, the entire contents of which areincorporated herein by reference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

Embodiments of the invention relate to a solar cell and a solar cellmodule.

2. Description of the Related Art

Recently, as existing energy sources such as petroleum and coal areexpected to be depleted, interests in alternative energy sources forreplacing the existing energy sources are increasing. Among thealternative energy sources, solar cells generating electric energy fromsolar energy have been particularly spotlighted.

A silicon solar cell generally includes a substrate and an emitterlayer, each of which is formed of a semiconductor, and a plurality ofelectrodes respectively formed on the substrate and the emitter layer.The semiconductors forming the substrate and the emitter layer havedifferent conductive types, such as a p-type and an n-type. A p-njunction is formed at an interface between the substrate and the emitterlayer.

When light is incident on the solar cell, a plurality of electron-holepairs are generated in the semiconductors. The electron-hole pairs areseparated into electrons and holes by the photovoltaic effect. Thus, theseparated electrons move to the n-type semiconductor (e.g., the emitterlayer) and the separated holes move to the p-type semiconductor (e.g.,the substrate), The electrons and holes are respectively collected bythe electrode electrically connected to the emitter layer and theelectrode electrically connected to the substrate. The electrodes areconnected to one another using electric wires to thereby obtain electricpower.

The electrode connected to the emitter layer and the electrode connectedto the substrate may be respectively positioned on an incident surfaceof the substrate on which light is incident and a surface of thesubstrate, opposite the incident surface, on which light is notincident. Alternatively, the electrode connected to the emitter layerand the electrode connected to the substrate may be positioned on thesurface of the substrate opposite the incident surface.

When all of the electrodes connected to the emitter layer and thesubstrate are positioned on the surface of the substrate opposite theincident surface, an incident area of light increases. Hence, efficiencyof the solar cell is improved.

SUMMARY OF THE INVENTION

Embodiments of the invention provide a solar cell capable of improvingan operational efficiency and a solar cell module including the solarcell.

In one aspect, there is a solar cell including a substrate of a firstconductive type, a plurality of emitter layers of a second conductivetype opposite the first conductive type, a plurality of first conductivemembers partially connected to the substrate, and a plurality of secondconductive members partially connected to each of the plurality ofemitter layers.

A first conductive member being an outermost one of the plurality offirst conductive members and a second conductive member being anoutermost one of the plurality of second conductive members may bepositioned on the same line.

Each of the plurality of first conductive members and each of theplurality of second conductive members may have a ball shape.

The plurality of emitter layers may be positioned in a surface of thesubstrate on which light is not incident.

The solar cell may further include a passivation layer positioned on theplurality of emitter layers.

The passivation layer may include a plurality of first openings exposingportions of each of the plurality of emitter layers. The plurality ofsecond conductive members may be positioned in the plurality of firstopenings and may be connected to the exposed portions of each of theplurality of emitter layers exposed through the plurality of firstopenings.

The solar cell may further include a plurality of surface field layersthat are positioned in the surface of the substrate, on which light isnot incident, to be spaced apart from the plurality of emitter layers.

The plurality of emitter layers and the plurality of surface fieldlayers may extend in the same direction in the surface of the substrateon which light is not incident.

Ends of the plurality of emitter layers and ends of the plurality ofsurface field layers may be positioned on the same line.

The passivation layer may further include a plurality of second openingsexposing portions of each of the plurality of surface field layers. Theplurality of first conductive members may be positioned in the pluralityof second openings and may be connected to the exposed portions of eachof the plurality of surface field layers exposed through the pluralityof second openings.

The solar cell may further include a plurality of first electrodes, thatare positioned in the plurality of first openings and are positionedbetween each of the plurality of emitter layers and the plurality ofsecond conductive members, and a plurality of second electrodes, thatare positioned in the plurality of second openings and are positionedbetween each of the plurality of surface field layers and the pluralityof first conductive members.

A first electrode being an outermost one of the plurality of firstelectrodes and a second electrode being an outermost one of theplurality of second electrodes may be positioned on the same line.

Each of the plurality of first electrodes and each of the plurality ofsecond electrodes may contain silver (Ag). Each of the plurality offirst electrodes and each of the plurality of second electrodes mayfurther contain at least one selected from the group consisting ofnickel (Ni), copper (Cu), aluminum (Al), tin (Sn), zinc (Zn), indium(In), titanium (Ti), gold (Au), and a combination thereof.

The plurality of first electrodes and the plurality of second electrodesmay be formed using at least one of a deposition method, a printingmethod, an electroplating method, and an electroless plating method.

Each of the plurality of first openings and each of the plurality ofsecond openings may have a rectangle shape.

The solar cell may further include a surface field layer of the firstconductive type positioned in a surface of the substrate on which lightis incident.

Each of the plurality of first conductive members and each of theplurality of second conductive members may be formed of SnPb-basedmaterial or Pb-free material.

The plurality of first conductive members and the plurality of secondconductive members may be formed using a deposition method or anelectroplating method.

The solar cell may further include a plurality of first electrodespositioned between the plurality of first conductive members and thesubstrate and a plurality of second electrodes positioned between theplurality of second conductive members and each of the plurality ofemitter layers.

The plurality of first electrodes and the plurality of first conductivemembers may be positioned in the same direction as the plurality ofsecond electrodes and the plurality of second conductive members.

In another aspect, there is a solar cell module having a plurality ofsolar cells each including a plurality of surface field layerspositioned in a substrate, a plurality of emitter layers positioned inthe substrate, a plurality of first conductive members partiallyconnected to each of the plurality of surface field layers, and aplurality of second conductive members partially connected to each ofthe plurality of emitter layers, first and second protective layers thatare positioned on opposite sides of the plurality of solar cells andprotect the plurality of solar cells, a transparent member positioned onthe first protective layer, and a back sheet underlying the secondprotective layer, the back sheet having a first electrode pattern part,that contacts the plurality of first conductive members of each of theplurality of solar cells to electrically connect the plurality of firstconductive members to one another, and a second electrode pattern partthat contacts the plurality of second conductive members of each of theplurality of solar cells to electrically connect the plurality of secondconductive members to one another.

The second protective layer may include a plurality of first openingsexposing the plurality of first conductive members of the plurality ofsolar cells and a plurality of second openings exposing the plurality ofsecond conductive members of the plurality of solar cells. The pluralityof first conductive members may contact the first electrode pattern partthrough the plurality of first openings, and the plurality of secondconductive members may contact the second electrode pattern part throughthe plurality of second openings.

The first electrode pattern part and the second electrode pattern partmay be positioned adjacent to each other and may be connected to eachother.

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying drawings, which are included to provide a furtherunderstanding of the invention and are incorporated in and constitute apart of this specification, illustrate embodiments of the invention andtogether with the description serve to explain the principles of theinvention. In the drawings:

FIG. 1 is a perspective view of a solar cell according to an embodimentof the invention;

FIG. 2 is a cross-sectional view taken along line II-II of FIG. 1;

FIG. 3 is a plan view of a back surface of the solar cell shown in FIG.1;

FIG. 4 is a plan view illustrating a plurality of first and secondimpurity regions in a back surface of a substrate of a solar cellaccording to an embodiment of the invention, a plurality of firstelectrodes on the first impurity regions, and a plurality of secondelectrodes on the second impurity regions;

FIG. 5 is a schematic cross-sectional view of a solar cell moduleaccording to an embodiment of the invention; and

FIG. 6 is a cross-sectional view of the solar cell module including onesolar cell obtained after laminating the solar cell module shown in FIG.5.

DETAILED DESCRIPTION OF THE EMBODIMENTS

The invention will be described more fully hereinafter with reference tothe accompanying drawings, in which example embodiments of theinventions are shown. This invention may, however, be embodied in manydifferent forms and should not be construed as limited to theembodiments set forth herein.

In the drawings, the thickness of layers, films, panels, regions, etc.,are exaggerated for clarity. Like reference numerals designate likeelements throughout the specification. It will be understood that whenan element such as a layer, film, region, or substrate is referred to asbeing “on” another element, it can be directly on the other element orintervening elements may also be present. In contrast, when an elementis referred to as being “directly on” another element, there are nointervening elements present. Further, it will be understood that whenan element such as a layer, film, region, or substrate is referred to asbeing “entirely” on another element, it may be on the entire surface ofthe other element and may not be on a portion of an edge of the otherelement.

Reference will now be made in detail to embodiments of the invention,examples of which are illustrated in the accompanying drawings.

A solar cell according to an embodiment of the invention is describedbelow in detail with reference to FIGS. 1 to 4.

FIG. 1 is a perspective view of a solar cell according to an embodimentof the invention. FIG. 2 is a cross-sectional view taken along lineII-II of FIG. 1. FIG. 3 is a plan view of a back surface of the solarcell shown in FIG. 1. FIG. 4 is a plan view illustrating a plurality offirst and second impurity regions in a back surface of a substrate of asolar cell according to an embodiment of the invention, a plurality offirst electrodes on the first impurity regions, and a plurality ofsecond electrodes on the second impurity regions.

As shown in FIGS. 1 and 2, a solar cell 1 according to an embodiment ofthe invention includes a substrate 110, a front surface field layer 120positioned in a surface (hereinafter, referred to as “a front surface”)of the substrate 110 on which light is incident, an anti-reflectionlayer 130 positioned on the front surface field layer 120, a pluralityof first impurity regions 141 positioned in a surface (hereinafter,referred to as “a back surface”) of the substrate 110, opposite thefront surface of the substrate 110, on which the light is not incident,a plurality of second impurity regions 142 that are positioned in theback surface of the substrate 110 to be spaced apart from the pluralityof first impurity regions 141, a back passivation layer 150 positionedon the first impurity regions 141 and the second impurity regions 142, aplurality of first electrodes 161 that are positioned on the pluralityof first impurity regions 141 and contact the plurality of firstimpurity regions 141, a plurality of second electrodes 162 that arepositioned on the plurality of second impurity regions 142 and contactthe plurality of second impurity regions 142, a plurality of firstsolder balls 171 connected to the plurality of first electrodes 161, anda plurality of second solder balls 172 connected to the plurality ofsecond electrodes 162.

The substrate 110 is a semiconductor substrate formed of firstconductive type silicon, for example, an n-type silicon, though notrequired. Examples of silicon include crystalline silicon, such assingle crystal silicon and polycrystalline silicon, and amorphoussilicon. If the substrate 110 is of the n-type, the substrate 110 maycontain impurities of a group V element such as phosphorus (P), arsenic(As), and antimony (Sb). Alternatively, the substrate 110 may be of ap-type. If the substrate 110 is of the p-type, the substrate 110 maycontain impurities of a group III element such as boron (B), gallium(Ga), and indium (In). Other semiconductor materials may be used for thesubstrate 110.

The front surface of the substrate 110 is textured to form a texturedsurface corresponding to an uneven surface. Hence, a light reflectanceof the front surface of the substrate 110 is reduced. Further, because alight incident operation and a light reflection operation are many timesperformed on the textured surface of the substrate 110, the light isconfined in the solar cell 1. Hence, a light absorption increases andthe efficiency of the solar cell 1 is improved. A plurality ofprotrusions of the textured surface may have a non-uniform pyramidstructure, and a height of each of the protrusions may be approximately1 μm to 10 μm. Hence, a light reflectance of the textured surface of thesubstrate 100 may be reduced to about 11%.

The front surface field layer 120 positioned in the front surface of thesubstrate 110 is formed by more heavily doping the substrate 110 withimpurities (e.g., n-type impurities) of the same conductive type as thesubstrate 110 than the substrate 110. Thus, the impurities of the sameconductive type as the substrate 110 may be impurities of a group Velement such as P, As, and Sb. Hence, the movement of carriers (e.g.,holes) around the surface of the substrate 110 is prevented or reducedby a potential barrier resulting from a difference between impurityconcentrations of the substrate 110 and the front surface field layer120. Thus, a recombination and/or a disappearance of electrons and holesaround the front surface of the substrate 110 are prevented or reduced.

The anti-reflection layer 130 on front surface field layer 120 is formedof silicon nitride (SiNx) and/or silicon oxide (SiO_(x)). Theanti-reflection layer 130 reduces a reflectance of light incident on thesubstrate 110 and increases a selectivity of a predetermined wavelengthband to thereby increase the efficiency of the solar cell 1. Theanti-reflection layer 130 may have a thickness of about 70 nm to 80 nm.The anti-reflection layer 130 has a single-layered structure in theembodiment of the invention, but may also have a multi-layered structuresuch as a double-layered structure. The anti-reflection layer 130 may beomitted, if desired.

The plurality of first impurity regions 141 and the plurality of secondimpurity regions 142 are positioned in the back surface of the substrate110 to be spaced apart from one another.

The plurality of first impurity regions 141 are spaced apart from oneanother and extend substantially parallel to one another in a fixeddirection. Each of the first impurity regions 141 is an impurity regionobtained by more heavily doping the substrate 110 with impurities (e.g.,n-type impurities) of the same conductive type as the substrate 110 thanthe substrate 110. Each of the first impurity regions 141 serves as aback surface field layer in the same manner as the front surface fieldlayer 120. Hence, carriers (e.g., holes) moving to the first impurityregions 141 are prevented or reduced from moving to the first electrodes161 by a potential barrier resulting from a difference between impurityconcentrations of the substrate 110 and the first impurity regions 141.Thus, a recombination and/or a disappearance of electrons and holesaround the first electrodes 161 are prevented or reduced.

The second impurity regions 142 are separated from the first impurityregions 141 and extend substantially parallel to one another in the samedirection as an extension direction of the first impurity regions 141.Hence, the first impurity regions 141 and the second impurity regions142 are alternately positioned in the back surface of the substrate 110.

Each of the second impurity regions 142 is an impurity region obtainedby heavily doping the substrate 110 with impurities (e.g., p-typeimpurities) of a second conductive type opposite the first conductivetype of the substrate 110. Each of the second impurity regions 142serves as an emitter layer, and thus the substrate 110 and the secondimpurity regions 142 form a p-n junction. Thus, the second impurityregions 142 contain impurities of a group III element such as B, Ga, andIn.

A plurality of electron-hole pairs produced by light incident on thesubstrate 110 are separated into electrons and holes by a built-inpotential difference resulting from the p-n junction between thesubstrate 110 and the second impurity regions 142 each serving as theemitter layer. Then, the separated electrons move to the n-typesemiconductor, and the separated holes move to the p-type semiconductor.Thus, when the substrate 110 is of the n-type and the second impurityregions 142 are of the p-type in the embodiment of the invention, theseparated electrons move to the first impurity regions 141 and theseparated holes move to the second impurity regions 142.

Because the substrate 110 and each of the second impurity regions 142form the p-n junction, the second impurity regions 142 may be of then-type if the substrate 110 is of the p-type unlike the embodiment ofthe invention described above. In this case, the separated electronsmove to the second impurity regions 142 and the separated holes move tothe first impurity regions 141.

The back passivation layer 150 on the first impurity regions 141 and thesecond impurity regions 142 has a plurality of first openings 181exposing a portion of each of the first impurity regions 141 and aplurality of second openings 182 exposing a portion of each of thesecond impurity regions 142. Each of the first and second openings 181and 182 has a rectangle shape. Other shapes may be used. For example,each of the first and second openings 181 and 182 may have variousshapes such as a circle and an oval.

The back passivation layer 150 may be formed of silicon nitride (SiNx)and/or silicon oxide (SiO_(x)). The back passivation layer 150 shows apassivation effect capable converting unstable bonds existing around thesurface of the substrate 110 into stable bonds to thereby prevent orreduce a recombination and/or a disappearance of carriers moving to theback surface of the substrate 110. Further, the back passivation layer150 reflects light passing through the substrate 110 inside the solarcell 1, so that light incident on the substrate 110 is not reflectedoutside the solar cell 1. Hence, an amount of light reflected outsidethe solar cell 1 is reduced.

The plurality of first electrodes 161 are positioned on the exposedportions of the plurality of first impurity regions 141 exposed throughthe plurality of first openings 181. The first electrodes 161 areelectrically and physically connected to the first impurity regions 141.

The plurality of second electrodes 162 are positioned on the exposedportions of the plurality of second impurity regions 142 exposed throughthe plurality of second openings 182. The second electrodes 162 areelectrically and physically connected to the second impurity regions142. Thus, because the first electrodes 161 are positioned along thefirst impurity regions 141 and the second electrodes 162 are positionedalong the second impurity regions 142, the first and second electrodes161 and 162 are positioned in the same direction, i.e., an extensiondirection of the first and second impurity regions 141 and 142.

The first and second electrodes 161 and 162 may be formed by depositinga conductive metal material and then patterning the deposited conductivemetal material or by directly performing an electroplating method or anelectroless plating method. A thermal process is performed on the firstand second electrodes 161 and 162, that are firstly formed using adeposition method or a plating method, under the hydrogen atmosphere, sothat the first and second electrodes 161 and 162 and the first andsecond impurity regions 141 and 142 form a low resistance ohmic contact.Because each of the firstly formed first and second electrodes 161 and162 is very thin, it is difficult to bring the first and second solderballs 171 and 172 respectively positioned on the very thin first andsecond electrodes 161 and 162 into electrical contact with the very thinfirst and second electrodes 161 and 162. Thus, the electroplating methodor the electroless plating method may be performed on the firstly formedfirst and second electrodes 161 and 162 to thereby increase thethickness of each of the firstly formed first and second electrodes 161and 162. In this case, the thickness of each of the first and secondelectrodes 161 and 162 may be approximately 3 μm to 150 μm.

The first and second electrodes 161 and 162 may be formed of silver (Ag)and at least one conductive metal material. Examples of the conductivemetal material include at least one selected from the group consistingof nickel (Ni), copper (Cu), aluminum (Al), tin (Sn), zinc (Zn), indium(In), titanium (Ti), gold (Au), and a combination thereof. Otherconductive metal materials may be used. For example, an ohmic contactbetween the silicon substrate 110 and aluminum (Al) may be formed usingAl as the at least one conductive metal material.

The first electrodes 161 collect carriers moving to the first impurityregions 141 electrically connected to the first electrodes 161 totransfer the carriers to the first solder balls 171. The secondelectrodes 162 collect carriers moving to the second impurity regions142 electrically connected to the second electrodes 162 to transfer thecarriers to the second solder balls 172.

In the embodiment of the invention, the plurality of first solder balls171 are positioned only on the plurality of first electrodes 161, andthe plurality of second solder balls 172 are positioned only on theplurality of second electrodes 162. The first and second solder balls171 and 172 are conductive members formed of a conductive material andmay be formed of SnPb-based material. Alternatively, the first andsecond solder balls 171 and 172 may be formed of a material obtained byreducing an amount of Pb contained in a general solder material orPb-free material obtained by removing Pb from the general soldermaterial, so as to prevent an environmental pollution resulting from Pb.

In the embodiment of the invention, the first and second solder balls171 and 172 have a ball shape. Other shapes such as a column shape maybe used.

The first and second solder balls 171 and 172 are respectively formed onat least a portion of the first electrode 161 and at least a portion ofthe second electrode 162 using a deposition method or an electroplatingmethod. Hence, the first and second solder balls 171 and 172 aregenerally positioned in the first and second openings 181 and 182.

The plurality of first solder balls 171 output carriers (e.g.,electrons) transferred through the plurality of first electrodes 161 tothe outside, and the plurality of second solder balls 172 outputcarriers (e.g., holes) transferred through the plurality of secondelectrodes 162 to the outside.

In the embodiment of the invention, because the first and secondimpurity regions 141 and 142 may be electrically connected to the firstand second solder balls 171 and 172 without the first and secondelectrodes 161 and 162, the first and second electrodes 161 and 162 maybe omitted. In this case, the first solder balls 171 are directlyconnected to the first impurity regions 141, and the second solder balls172 are directly connected to the second impurity regions 142. Thus,carriers moving to the first and second impurity regions 141 and 142 arecollected by the first and second solder balls 171 and 172 and then areoutput to the outside.

As shown in FIG. 3, the first and second solder balls 171 and 172 areused to electrically connect the first and second impurity regions 141and 142 to an external device and to perform a point contact in whichthe first and second solder balls 171 and 172 are partially connected tothe first and second impurity regions 141 and 142 through the first andsecond electrodes 161 and 162. Hence, a bending of the substrate 110resulting from the first and second electrodes 161 and 162 and the firstand second solder balls 171 and 172 positioned on the back surface ofthe substrate 110 or a bending of the substrate 110 resulting from adifference between thermal expansion coefficients between the substrate110 and the elements 161, 162, 171, and 172 are prevented or reduced.

In a solar cell according to a comparative example, a plurality of firstelectrodes are straightly formed along a plurality of first impurityregions and have a stripe shape, and a plurality of second electrodesare straightly formed along a plurality of second impurity regions andhave a stripe shape. In other words, each first electrode is straightlypositioned along each first impurity region, and each second electrodeis straightly positioned along each second impurity region. Hence, aformation area of each first electrode almost overlaps a formation areaof each first impurity region, and a formation area of each secondelectrode almost overlaps a formation area of each second impurityregion.

On the other hand, in the solar cell according to the embodiment of theinvention, the first and second electrodes 161 and 162 are positionedonly in the first and second openings 181 and 182, and the first andsecond solder balls 171 and 172 are positioned only in the first andsecond openings 181 and 182. Hence, each first electrode 161 and eachfirst solder ball 171 overlap only at an exposed portion of the firstimpurity region 141 exposed through the first openings 181, and eachsecond electrode 162 and each second solder ball 172 overlap only at anexposed portion of the second impurity region 142 exposed through thesecond openings 182. In other words, the plurality of first electrodes161 are positioned on each first impurity region 141 to be spaced apartfrom one another at a constant distance, and the plurality of secondelectrodes 162 are positioned on each second impurity region 142 to bespaced apart from one another at a constant distance. Further, theplurality of first solder balls 171 are positioned on the plurality offirst electrodes 161, and the plurality of second solder balls 172 arepositioned on the plurality of second electrodes 162. Hence, formationareas of the first and second electrodes 161 and 162 and formation areasof the first and second solder balls 171 and 172 are greatly reduced,compared with the solar cell according to the comparative example.

Accordingly, because the formation areas of the first and secondelectrodes 161 and 162 on the back surface of the substrate 110 aregreatly reduced, the weight of the first and second electrodes 161 and162 and the weight of the first and second solder balls 171 and 172 aregreatly reduced, or the bending of the substrate 110 resulting from thedifference between the thermal expansion coefficients between thesubstrate 110 and the elements 161, 162, 171, and 172 are greatlyreduced, compared with the solar cell according to the comparativeexample. Further, because the solder balls 171 and 172 are formedinstead of a stripe-shaped electrode or a bus bar, a thickness of thesolar cell 1 is reduced. As a result, the weight of the solar cell 1 isreduced.

In the embodiment of the invention, the first and second solder balls171 and 172 in addition to the first and second electrodes 161 and 162are further formed on the back surface of the substrate 110, comparedwith the solar cell according to the comparative example. However,because a sum of the weight of the first and second electrodes 161 and162 and the weight of the first and second solder balls 171 and 172 ismuch less than the weight of the electrodes in the comparative example,the bending of the substrate 110 is prevented or reduced.

The solar cell according to the comparative example includes a first busbar, that extends in a direction crossing the stripe-shaped firstelectrodes to connect the stripe-shaped first electrodes to one another,and a second bus bar that extends in a direction crossing thestripe-shaped second electrodes to connect the stripe-shaped secondelectrodes to one another. The first and second bus bars are generallypositioned at an edge of the substrate and are opposite to each other.The first and second bus bars collect all of carriers moving along eachfirst electrode and each second electrode to output the carriers to theoutside.

However, the solar cell 1 according to the embodiment of the inventiondoes not include a first bar for electrically connecting the firstsolder balls 171 to one another and a second bar for electricallyconnecting the second solder balls 172 to one another. Hence, as shownin FIG. 4, because the first and second impurity regions 141 and 142 areformed in an area of the substrate 110 (for example, an edge of thesubstrate 110) for the first and second bus bars, formation areas of thefirst and second impurity regions 141 and 142 increase. As a result, theefficiency of the solar cell 1 increases.

Furthermore, because the first and second bus bars are not formed,locations of ends of the first and second impurity regions 141 and 142are substantially the same as each other. More specifically, as shown inFIG. 4, left ends of the first and second impurity regions 141 and 142are positioned on the same line L1, and right ends of the first andsecond impurity regions 141 and 142 are positioned on the same line L2.Further, a location of an end of the last first electrode 161 in anextension direction of the first electrodes 161 (for example, theleftmost first electrode or the rightmost first electrode in theextension direction of the first electrodes 161 in FIG. 4) issubstantially the same as a location of an end of the last secondelectrode 162 in an extension direction of the second electrodes 162(for example, the leftmost second electrode or the rightmost secondelectrode in the extension direction of the second electrodes 162 inFIG. 4). In this case, left ends of the first and second electrodes 161and 162 are positioned on the same line L11, and right ends of the firstand second electrodes 161 and 162 are positioned on the same line L21.All of the lines L1, L11, L2, L21 shown in FIG. 4 are linessubstantially perpendicular to a transverse direction of the substrate110. The solar cell 1 having the above-described structure is a backcontact solar cell in which the second impurity regions 142, the secondelectrodes 162, and the second solder balls 172 are positioned in theback surface of the substrate 110 on which light is not incident. Anoperation of the back contact solar cell 1 is described below.

When light irradiated to the solar cell 1 is incident on the substrate110 through the anti-reflection layer 130 and the front surface fieldlayer 120, a plurality of electron-hole pairs are generated in thesubstrate 110 by light energy based on the incident light. Further, areflection loss of light incident on the substrate 110 decreases becauseof the textured surface of the substrate 110 and the anti-reflectionlayer 130, and thus an amount of the light incident on the substrate 110further increases. The electron-hole pairs are separated from oneanother by the p-n junction between the substrate 110 and the secondimpurity regions 142, and the separated electrons move to the n-typefirst impurity regions 141 and the separated holes move to the p-typesecond impurity regions 142. The electrons moving to the first impurityregions 141 are collected by the first electrodes 161 and then areoutput to an external device through the first solder balls 171, and theholes moving to the second impurity regions 142 are collected by thesecond electrodes 162 and then are output to the external device throughthe second solder balls 172.

In the embodiment of the invention, because the first and secondelectrodes 161 and 162, which prevent light from being incident on thesubstrate 110, are positioned on the back surface of the substrate 110,an amount of light incident on the substrate 110 increases. Hence, aseries resistance of the solar cell 1 is reduced, and thus theefficiency of the solar cell 1 is improved. Further, an amount ofcarriers recombined by the front surface field layer 120 and the backpassivation layer 150 is reduced, and thus the efficiency of the solarcell 1 is further improved.

Furthermore, because the solar cell 1 according to the embodiment of theinvention does not include the bus bars, formation locations of thefirst and second impurity regions 141 and 142 extend to what would bethe formation locations of the bus bars. Further, formation locations ofthe first solder balls 171 and the first electrodes 161 connected to thefirst impurity regions 141 and formation locations of the second solderballs 172 and the second electrodes 162 connected to the second impurityregions 142 extend. Thus, a generation amount of carriers increasesbecause of an increase in the formation areas of the first and secondimpurity regions 141 and 142, and also a collection amount of carriersincreases because the formation locations of the first and second solderballs 171 and 172 and the formation locations of the first and secondelectrodes 161 and 162 extend. As a result, the efficiency of the solarcell 1 is further improved.

Although the above-described solar cell 1 may be individually used, theplurality of solar cells 1 having the same structure may be electricallyconnected to one another to form a solar cell module for more efficientuse of the solar cells 1. As described above, the solar cell 1 does notinclude the first bar for electrically connecting the first solder balls171 to one another and the second bar for electrically connecting thesecond solder balls 172 to one another. Thus, the solar cell moduleincluding the plurality of solar cells 1 includes a conductive patternused to electrically connect the first solder balls 171 of each solarcell 1 to one another and to electrically connect the second solderballs 172 of each solar cell 1 to one another.

A solar cell module according to an embodiment of the invention isdescribed below with reference to FIGS. 5 and 6.

FIG. 5 is a schematic cross-sectional view of a solar cell moduleaccording to an embodiment of the invention. FIG. 6 is a cross-sectionalview of the solar cell module including one solar cell obtained afterlaminating the solar cell module shown in FIG. 5.

As shown in FIG. 5, a solar cell module 200 according to an embodimentof the invention includes a solar cell 1, protective layers 210 and 220for protecting the solar cell 1, a transparent member 230 on theprotective layer 210 (hereinafter, referred to as “upper protectivelayer”) positioned on a light receiving surface of the solar cell 1, aninsulating layer 240 underlying the protective layer 220 (hereinafter,referred to as “lower protective layer”) positioned on a surface,opposite the light receiving surface, on which light is not incident,and a back sheet 250 underlying the insulating layer 240.

Although FIG. 5 illustrates only one solar cell 1 of the solar cellmodule 200, the solar cell module 200 includes the plurality of solarcells 1. The plurality of solar cells 1 are arranged in a matrixstructure and are connected in series or in parallel to one another.

The upper and lower protective layers 210 and 220 prevent corrosion ofmetal resulting from the moisture penetration and protect the solar cellmodule 200 from an impact. The upper and lower protective layers 210 and220 and the solar cell 1 form an integral body when a lamination processis performed in a state where the upper and lower protective layers 210and 220 are respectively positioned on and under the solar cell 1. Theupper and lower protective layers 210 and 220 may be formed of ethylenevinyl acetate (EVA), for example. The lower protective layer 220 has aplurality of openings 21 and 22 corresponding to a plurality of firstopenings 181 and a plurality of second openings 182.

The transparent member 230 on the upper protective layer 210 may beformed of a tempered glass having a high transmittance capable ofpreventing a damage. The tempered glass may be a low iron tempered glasscontaining a small amount of iron. The transparent member 230 may havean embossed inner surface so as to increase a scattering effect oflight.

The insulating layer 240 on the back sheet 250 has a plurality ofopenings 41 and 42. The plurality of openings 41 are positioned atlocations corresponding to the plurality of openings 21 of the lowerprotective layer 220, and the plurality of openings 42 are positioned atlocations corresponding to the plurality of openings 22 of the lowerprotective layer 220. The insulating layer 240 electrically insulatesbetween the lower protective layer 220 and the back sheet 250. Theinsulating layer 240 is omitted, if desired.

Thus, the plurality of openings 41 and 21 substantially overlap theplurality of openings 181, and the plurality of openings 42 and 22substantially overlap the plurality of openings 182. As a result, theopenings 41 and 21 have substantially the same shape as the openings181, and the openings 42 and 22 have substantially the same shape as theopenings 182. On the contrary, each of the openings 41, 21, 42, and 22may have a stripe shape at locations corresponding to solder balls 171and 172 positioned along the corresponding impurity regions 141 and 142.In other words, the openings 41, 21, 42, and 22 may be positioned on thelower protective layer 220 and the insulating layer 240 at locationscorresponding to the impurity regions 141 and 142.

The back sheet 250 prevents moisture or oxygen from penetrating into aback surface of the solar cell module 200 to protect the solar cells 1from an external environment. The back sheet 250, as shown in FIG. 5,includes a pattern part 255, i.e., a conductive pattern including aplurality of first electrode patterns 251 and a plurality of secondelectrode patterns 252.

A shape of each first electrode pattern 251 is determined based on alocation shape of each first solder ball 171 of the solar cell 1, and ashape of each second electrode pattern 252 is determined based on alocation shape of each second solder ball 172 of the solar cell 1.

As a result, the first solder balls 171 contact the first electrodepatterns 251 passing through the openings 21 and 41 and are electricallyconnected to one another through the first electrode patterns 251. Thesecond solder balls 172 contact the second electrode patterns 252passing through the openings 22 and 42 and are electrically connected toone another through the second electrode patterns 252.

The adjacent first and second electrode patterns 251 and 252 areconnected to each other. In other words, in plurality of solar cells 1positioned on the same row, the first electrode patterns 251corresponding to one solar cell 1 is connected to the second electrodepatterns 252 corresponding to a solar cell 1 adjacent to the one solarcell 1, and the second electrode patterns 252 corresponding to the onesolar cell 1 is connected to the first electrode patterns 251corresponding to another solar cell 1 adjacent to the one solar cell 1.For example, the first solder balls 171 of a first solar cell 1 of twoadjacent solar cells 1 positioned on the same row are electricallyconnected to the second solder balls 172 of a second solar cell 1 of thetwo adjacent solar cells 1. Further, the second solder balls 172 of thefirst solar cell 1 are electrically connected to the first solder balls171 of a third solar cell 1 positioned prior to the first solar cell 1,and the first solder balls 171 of the second solar cell 1 areelectrically connected to the second solder balls 172 of a fourth solarcell 1 following the second solar cell 1. As a result, the solar cells 1arranged in the matrix structure are electrically connected in series toone another.

The pattern part 255 of the back sheet 250 may be formed in a desiredform by attaching a metal thin plate such as copper (Cu) to the backsheet 250 and then patterning the metal thin plate depending onformation locations of the first and second solder balls 171 and 172.

In the solar cell module 200, carriers transferred by the first andsecond solder balls 171 and 172 of each solar cell 1 are collected bythe pattern part 255, and also the plurality of solar cells 1 arrangedin the matrix structure are connected in series or in parallel to oneanother through the pattern part 255. Hence, carriers collected by theplurality of solar cells 1 are finally output to an external device.

Although FIG. 5 illustrates the pattern part 255 positioned inside theback sheet 250, the pattern part 255 may be positioned on the back sheet250.

The back sheet 50 may have a multi-layered structure including amoisture/oxygen penetrating prevention layer, a chemical corrosionprevention layer, an insulation layer, etc.

A method for manufacturing the solar cell module 200 may sequentiallyinclude testing the plurality of solar cells 1, arranging the testedsolar cells 1 in the matrix structure, disposing the elements 210, 220,230, 240, 250, and 1 in fixed order, more particularly successivelydisposing the back sheet 250 including the pattern part 255, theinsulating layer 240, the lower protective layer 220, the plurality ofsolar cells 1, the upper protective layer 210, and the transparentmember 230 from the bottom of the solar cell module 200 in the ordernamed, performing a lamination process in a vacuum state to form anintegral body of the elements 210, 220, 230, 240, 250, and 1 (refer toFIG. 6), performing an edge trimming process to remove an unnecessaryportion, testing the solar cell module 200, and the like.

When a misalignment between the plurality of solar cells 1 and the backsheet 250 occurs, a bad contact between the solder balls 171 and 172 andthe pattern part 255 is prevented because of the insulating layer 240.

As above, because the pattern part 255 directly contacting the solderballs 171 and 172 is formed in the back sheet 250, a distance rangingfrom the impurity regions 141 and 142 to the pattern part 255 of theback sheet 250 is greatly reduced to several hundreds of micrometers(μm). Hence, the efficiency of the solar cell module 200 is improvedbecause of a reduction in a wiring resistance.

Although the explanation was given of an example of the solar cell, inwhich both the first and second electrodes 161 and 162 are positioned onthe back surface of the substrate 110, in the embodiments of theinvention, the embodiments of the invention may be applied to varioussolar cells. For example, the embodiments of the invention may beapplied to a solar cell in which the plurality of first electrodes 161are positioned on the front surface of the substrate 110 and theplurality of second electrodes 162 are positioned on the back surface ofthe substrate 110.

Although embodiments have been described with reference to a number ofillustrative embodiments thereof, it should be understood that numerousother modifications and embodiments can be devised by those skilled inthe art that will fall within the scope of the principles of thisdisclosure. More particularly, various variations and modifications arepossible in the component parts and/or arrangements of the subjectcombination arrangement within the scope of the disclosure, the drawingsand the appended claims. In addition to variations and modifications inthe component parts and/or arrangements, alternative uses will also beapparent to those skilled in the art.

1. A solar cell, comprising: a substrate of a first conductive type; aplurality of emitter layers of a second conductive type opposite thefirst conductive type; a plurality of first conductive members partiallyconnected to the substrate; and a plurality of second conductive memberspartially connected to each of the plurality of emitter layers.
 2. Thesolar cell of claim 1, wherein a first conductive member being anoutermost one of the plurality of first conductive members and a secondconductive member being an outermost one of the plurality of secondconductive members are positioned on the same line.
 3. The solar cell ofclaim 1, wherein each of the plurality of first conductive members andeach of the plurality of second conductive members have a ball shape. 4.The solar cell of claim 1, wherein the plurality of emitter layers arepositioned in a surface of the substrate on which light is not incident.5. The solar cell of claim 4, further comprising a passivation layerpositioned on the plurality of emitter layers.
 6. The solar cell ofclaim 5, wherein the passivation layer comprises a plurality of firstopenings exposing portions of each of the plurality of emitter layers,and the plurality of second conductive members are positioned in theplurality of first openings and are connected to the exposed portions ofeach of the plurality of emitter layers exposed through the plurality offirst openings.
 7. The solar cell of claim 6, further comprising aplurality of surface field layers that are positioned in the surface ofthe substrate, on which light is not incident, to be spaced apart fromthe plurality of emitter layers.
 8. The solar cell of claim 7, whereinthe plurality of emitter layers and the plurality of surface fieldlayers extend in the same direction in the surface of the substrate onwhich light is not incident.
 9. The solar cell of claim 8, wherein endsof the plurality of emitter layers and ends of the plurality of surfacefield layers are positioned on the same line.
 10. The solar cell ofclaim 7, wherein the passivation layer further comprises a plurality ofsecond openings exposing portions of each of the plurality of surfacefield layers, and the plurality of first conductive members arepositioned in the plurality of second openings and are connected to theexposed portions of each of the plurality of surface field layersexposed through the plurality of second openings.
 11. The solar cell ofclaim 10, further comprising a plurality of first electrodes, that arepositioned in the plurality of first openings and are positioned betweeneach of the plurality of emitter layers and the plurality of secondconductive members, and a plurality of second electrodes, that arepositioned in the plurality of second openings and are positionedbetween each of the plurality of surface field layers and the pluralityof first conductive members.
 12. The solar cell of claim 11, wherein afirst electrode being an outermost one of the plurality of firstelectrodes and a second electrode being an outermost one of theplurality of second electrodes are positioned on the same line.
 13. Thesolar cell of claim 11, wherein each of the plurality of firstelectrodes and each of the plurality of second electrodes contain silver(Ag).
 14. The solar cell of claim 13, wherein each of the plurality offirst electrodes and each of the plurality of second electrodes furthercontain at least one selected from the group consisting of nickel (Ni),copper (Cu), aluminum (Al), tin (Sn), zinc (Zn), indium (In), titanium(Ti), gold (Au), and a combination thereof.
 15. The solar cell of claim11, wherein the plurality of first electrodes and the plurality ofsecond electrodes are formed using at least one of a deposition method,a printing method, an electroplating method, and an electroless platingmethod.
 16. The solar cell of claim 10, wherein each of the plurality offirst openings and each of the plurality of second openings have arectangle shape.
 17. The solar cell of claim 1, further comprising asurface field layer of the first conductive type positioned in a surfaceof the substrate on which light is incident.
 18. The solar cell of claim1, wherein each of the plurality of first conductive members and each ofthe plurality of second conductive members are formed of SnPb-basedmaterial or Pb-free material.
 19. The solar cell of claim 1, wherein theplurality of first conductive members and the plurality of secondconductive members are formed using a deposition method or anelectroplating method.
 20. The solar cell of claim 1, further comprisinga plurality of first electrodes positioned between the plurality offirst conductive members and the substrate and a plurality of secondelectrodes positioned between the plurality of second conductive membersand each of the plurality of emitter layers.
 21. The solar cell of claim20, wherein the plurality of first electrodes and the plurality of firstconductive members are positioned in the same direction as the pluralityof second electrodes and the plurality of second conductive members. 22.A solar cell module, comprising: a plurality of solar cells each havinga plurality of surface field layers positioned in a substrate, aplurality of emitter layers positioned in the substrate, a plurality offirst conductive members partially connected to each of the plurality ofsurface field layers, and a plurality of second conductive memberspartially connected to each of the plurality of emitter layers; firstand second protective layers that are positioned on opposite sides ofthe plurality of solar cells and protect the plurality of solar cells; atransparent member positioned on the first protective layer; and a backsheet underlying the second protective layer, the back sheet having afirst electrode pattern part, that contacts the plurality of firstconductive members of each of the plurality of solar cells toelectrically connect the plurality of first conductive members to oneanother, and a second electrode pattern part that contacts the pluralityof second conductive members of each of the plurality of solar cells toelectrically connect the plurality of second conductive members to oneanother.
 23. The solar cell module of claim 22, wherein the secondprotective layer comprises a plurality of first openings exposing theplurality of first conductive members of the plurality of solar cellsand a plurality of second openings exposing the plurality of secondconductive members of the plurality of solar cells, and the plurality offirst conductive members contact the first electrode pattern partthrough the plurality of first openings, and the plurality of secondconductive members contact the second electrode pattern part through theplurality of second openings.
 24. The solar cell module of claim 22,wherein the first electrode pattern part and the second electrodepattern part are positioned adjacent to each other and are connected toeach other.